The fabrication of modern circuits typically involves several steps. Integrated circuits are first fabricated on a semiconductor wafer, which contains multiple duplicated semiconductor chips, each including integrated circuits. The semiconductor chips are then sawed from the wafer and packaged. The packaging processes have two main purposes: to protect the semiconductor chips and connect interior integrated circuits to exterior pins.
With the increasing demand for more functions, Package-on-Package (PoP) technology, in which two or more packages are bonded in order to expand the integration ability of the packages, was developed. With a high degree of integration, the electrical performance of the resulting PoP package can be improved benefiting from the shortened connecting paths between components. By using the PoP technology, package design becomes more flexible and less complex. Time-to-market is also reduced.